This exception can occur especially when you have created a process, dragged an XDP form from the repository in Workbench to the variables view to create a variable. It will automatically create an xfaForm type variable, and use the Default Render service.

Reason

The Default Render service does not render XDP forms, only PDFs.

Solution

You must change the render properties manually for the xfaForm variable and choose another render service.

In this case the problem was that dragging an XDP from the repository to the variables view in Workbench used the Default Render Service to render the form. The Default Render Service only renders PDF forms, not XDP forms, and therefore the error above occurred.

If that is not exactly the same situation for you, then it may be a new issue, but I would still suspect a problem in the render settings you are using to render the form. The ALC-WKS-005-028 error code is a rather generic error to cover the various problems that can occur when configuring the render settings for a form.

You should refer to the Workbench documentation for your specific LiveCycle version to check/configure the render settings. You can also find Quick Starts in the Workbench docs which show how to setup the render settings for simple forms.